Aromatic monomer- and conjugated polymer-metal complexes

ABSTRACT

A halogenated aromatic monomer-metal complex useful for preparing a polymer for electronic devices such as a light-emitting diode (LED) device is described. The aromatic monomer-metal complex is designed to include a linking group that disrupts conjugation, thereby advantageously reducing or preventing electron delocalization between the aromatic monomer fragment and the metal complex fragment. Disruption of conjugation is often desirable to preserve the phosphorescent emission properties of the metal complex in a polymer formed from the aromatic monomer-metal complex. The resultant conjugated electroluminescent polymer has precisely controlled metal complexation and electronic properties that are substantially or completely independent of those of the polymer backbone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No. 12/718,238filed Mar. 5, 2010, which is a Divisional of U.S. application Ser. No.10/893,182 filed Jul. 16, 2004, which claims the benefit of U.S.Provisional Application No. 60/492,434 filed Aug. 4, 2003. The entiredisclosures of the prior applications are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

The present invention relates to an aromatic monomer-metal complex, anaromatic polymer-metal complex, which can be prepared from themonomer-metal complex, and an organic electronic device that contains afilm of the polymer-metal complex.

Organic electronic devices are found in a variety of electronicequipment. In such devices, an organic active layer is sandwichedbetween two electrical contact layers; the active layer emits light uponapplication of a voltage bias across the contact layers.

Polymers containing pendant metal-complex groups constitute a class ofpolymers suitable for light emitting applications, particularly inactive matrix driven polymeric LED displays. These polymers can beprepared, for example, by first polymerizing a monomer containing aligand capable of complexing with a metal, then contacting the polymerwith an organometallic complexing compound to insert the metal centerinto the polymer bound ligand. For example, in Macromolecules, Vol. 35,No. 19, 2002, Pei et al. describes a conjugated polymer with pendantbipyridyl groups directly coordinating with various Eu⁺³ α,β-diketones.

Similarly, in WO 02/31896, pp 17-18, Periyasamy et al. describeslanthanide metal-complexed polymers prepared by either a one- ortwo-step synthetic route. In the one-step route, an ML_(n) emitter isreacted with a polymer having metal-reactive functionality (X) to form apolymer with pendant —X-ML_(n-1) groups. In the two-step route, apolymer with pendant hydroxyethyl functionality is first condensed witha bipyridyl compound containing carboxylic acid functionality to form apolymer containing bipyridyl ester functionality (X-L′), which is thenreacted with ML_(n) to form a polymer with pendant X-L′-ML_(n-1)functionality.

One of the problems with these metal complexed electroluminescentpolymers is the incomplete reaction of pendant ligands with the metalcomplexing reagent. This inefficient coupling results inunpredictability of the properties of the final polymer due to thedifficulty in controlling the degree of metal-ligand complexation.Accordingly, it would be advantageous to prepare a luminescent polymerwith precisely controlled metal complexation.

SUMMARY OF THE INVENTION

The present invention addresses a need by providing in one aspect ahalogenated aromatic monomer-metal complex compound comprising ahalogenated aromatic monomer fragment and a metal complex fragment andrepresented by the following structure:

where L is a bidentate ligand; M is Ir, Rh, or Os; Ar′ and Ar″ arearomatic moieties which may be the same or different with the provisothat at least one of Ar′ and Ar″ is heteroaromatic; and wherein R_(a)and R_(b) are each independently a monovalent substitutent or H, withthe proviso that at least one of R_(a) and R_(b) contains a halogenatedaromatic monomer fragment and a linking group that disrupts conjugationbetween the halogenated aromatic monomer fragment and the metal complexfragment.

In a second aspect, the present invention is an electroluminescentpolymer having a backbone comprising a) structural units of an aromaticmonomer-metal complex having an aromatic fragment and a metal complexfragment, which structural units are represented by the followingformula:

where L is a bidentate ligand; M is Ir, Rh, or Os; Ar′ and Ar″ arearomatic moieties which may be the same or different with the provisothat at least one of Ar′ and Ar″ is heteroaromatic; and wherein R′_(a)and R′_(b) are substitutents or H, with the proviso that at least one ofR′_(a) and R′_(b) contains an aromatic group that is part of the polymerbackbone and a linking group that disrupts conjugation between thearomatic group and the metal complex fragment; and b) structural unitsof at least one aromatic comonomer, which polymer is characterized bybeing conjugated along a polymer backbone created by structural units ofthe aromatic monomer-metal complex and structural units of the at leastone aromatic comonomer.

In a third aspect, the present invention is an electronic devicecomprising a thin film of a luminescent polymer sandwiched between ananode and a cathode, which luminescent polymer has a backbone with a)structural units of an aromatic monomer-metal complex, which structuralunits are represented by the following formula:

where L is a bidentate ligand; M is Ir, Rh, or Os; Ar′ and Ar″ arearomatic moieties which may be the same or different with the provisothat at least one of Ar′ and Ar″ is heteroaromatic; and wherein R′_(a)and R′_(b) are substitutents or H, with the proviso that at least one ofR′_(a) and R′_(b) contains an aromatic group that is part of the polymerbackbone and a linking group that disrupts conjugation between thearomatic group and the metal complex fragment; and b) structural unitsof at least one aromatic comonomer, which polymer is characterized bybeing conjugated along a polymer backbone created by structural units ofthe aromatic monomer-metal complex and structural units of the at leastone aromatic comonomer.

The present invention addresses a need in the art by providing a simpleway of preparing a conjugated electroactive polymer with preciselycontrolled metal complexation. Moreover, the metal complex groups haveelectronic and/or luminescent properties that are minimally affected bythe conjugated polymer backbone.

DETAILED DESCRIPTION OF THE INVENTION

The first aspect of the present invention is a composition comprising ahalogenated aromatic monomer-metal complex having a halogenated aromaticmonomer fragment and a metal complex fragment and represented by thefollowing formula:

where L is a bidentate ligand; M is Ir, Rh, or Os; Ar′ and Ar″ arearomatic moieties which may be the same or different with the provisothat at least one of Ar′ and Ar″ is heteroaromatic; and wherein R_(a)and R_(b) are each independently a monovalent substitutent or H, withthe proviso that at least one of R_(a) and R_(b) contains a halogenatedaromatic monomer fragment and a linking group that disrupts conjugationbetween the aromatic monomer fragment and the metal complex fragment.

The halogenated aromatic monomer-metal complex of the present inventioncan be thought of as comprising a metal complex fragment and one or morehalogenated aromatic monomer fragments as illustrated:

R_(a) is X_(m)Ar-G- and R_(b) is X_(n)Ar-G-; each Ar is independently anaromatic group; each G is independently a divalent linking group thatdisrupts conjugation between Ar and Ar′—Ar″, preferably alkylene, O, S,carbonyl, SiR₂, where R is a substituent, or oxyalkylene, morepreferably methylene, oxymethylene, or O; each X is independently ahalogen group, preferably, each X is chloro or bromo; the sum of m+n isa positive integer, preferably 1 or 2; more preferably 1; and the sum ofo+p is a positive integer, preferably 1 or 2, more preferably 1. When o(or p) is 0, R_(a) (or R_(b)) can be any substituent including H. Thus,it is most preferred that each Ar′—Ar″ ligand contain onemonohalogenated aromatic substituent separated from Ar′—Ar″ byconjugation disrupting group.

The ligand Ar′—Ar″ is attached at least one substituent that is apolymerizable aromatic monomer separated from the ligand by a divalentlinking group. Examples of suitable substituted Ar′—Ar″ ligands include,but are not restricted to 2-phenylpyridines, 2-benzylpyridines,2-(2-thienyl)pyridines, 2-(2-furanyl)pyridines, 2,2′-dipyridines,2-benzo[b]thien-2-yl-pyridines, 2-phenylbenzothiazoles,2-(1-naphthalenyl)benzothiazoles, 2-(1-anthracenyl)benzothiazoles,2-phenylbenzoxazoles, 2-(1-naphthalenyl)benzoxazoles,2-(1-anthracenyebenzoxazoles, 2-(2-naphthalenyl)benzothiazoles,2-(2-anthracenyl)benzothiazoles, 2-(2-naphthalenyl)benzoxazoles,2-(2-anthracenyl)benzoxazoles, 2-(2-thienyl)benzothiazoles,2-(2-furanyl)benzothiazoles, 2-(2-thienyl)benzoxazoles,2-(2-furanyl)benzoxazoles, benzo[h]quinolines, 2-phenylquinolines,2-(2-naphthalenyl)quinolines, 2-(2-anthracenyl)quinolines,2-(1-naphthalenyl)quinolines, 2-(1-anthracenyl)quinolines,2-phenylmethylpyridines, 2-phenoxypyridines, 2-phenylthiopyridines,phenyl-2-pyridinylmethanones, 2-ethenylpyridines, 2-benzenemethanimines,2-(pyrrol-2-yl)pyridines, 2-(imidazol-2-yl)-pyridines,2-phenyl-1H-imidazoles, and 2-phenylindoles.

As used herein, “aromatic compounds” includes both aromatic andheteroaromatic compounds unless otherwise stated. Similarly, the term“aryl” is used herein to include both aryl and heteroaryl groups orcompounds unless otherwise stated.

The divalent linking group G contains a linking group or atom thatdisrupts conjugation, thereby inhibiting electron delocalization betweenthe aromatic monomer fragment and the metal complex fragment. Thisdisruption of conjugation between the fragments results in a similardisruption between the complex and the conjugated polymer backboneformed from the aromatic monomer fragment. Disruption of conjugation isoften desirable to preserve the light emission properties of the metalcomplex in a polymer formed from the aromatic monomer-metal complex.Such properties could be disadvantageously perturbed if electrons aredelocalized between the conjugated polymer backbone and the complex.

The linking group is preferably a substituted or unsubstitutednon-conjugated linear, branched, or cyclohydrocarbylene group or adivalent heteroatom or combinations. thereof. Examples of linking groupsinclude, alone or in combination, alkylene or cycloalkyl groups such asmethylene, ethylene, propylene, isopropylene, butylene, isobutylene,t-butylene, cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups;and heteroatoms such as oxygen and sulfur atoms and R—Si—R, carbonyl,and amine groups, except for triaryl amines. Preferred linking groupsinclude an oxygen atom and methylene and oxymethylene groups. As usedherein, “oxymethylene” refers to —OCH₂— or —CH₂O—groups.

General Procedure for Preparation of a Bis(Monohalogenated Aromatic)Monomer-Metal Complex

A halogenated aromatic monomer-metal complex containing abis(monohalogenated aromatic) fragment attached to a metal complexthrough a linking group can be prepared by a 4-step process, as shown:

G is as previously defined and is preferably O, methylene, oroxymethylene; Ar, Ar′, and Ar″ are each independently aromatic moietieswith the proviso that at least one of Ar′ and Ar″ is heteroaromatic.Preferably, Ar is a non-heteroaromatic moiety including a benzene, anaphthalene, or an anthracene moiety, more preferably a benzene moiety.Preferably, Ar′ and Ar″ are each independently selected from the groupconsisting of benzene, pyridine, thiophene, and fluorene moieties thatare complexed with the metal so as to form a 5-membered ring. Morepreferably one of Ar′ and Ar″ is a benzene moiety and the other of a Ar′and Ar″ is pyridine moiety.

X is halo, X′ and X″ are each independently halogen, boronate, —ZnCl,—ZnBr, —MgCl, MgBr, or—Sn(C₁₋₁₀-alkyl)₃, with the proviso that one of X′and X″ is halogen and the other of X′ and X″ is boronate, —ZnCl, —ZnBr,—MgCl, MgBr, or—Sn(C₁₋₁₀-alkyl)₃; X′″ is halogen, hydroxy, or alkoxy,preferably chloro, bromo, methoxy, or ethoxy, more preferably chloro orbromo. Where X′″ is halogen, the addition of the hydroxide or alkoxidebase is not necessary; where X′″ is hydroxy or alkoxy, the addition of ahydroxide or alkoxide base is preferred.

L is a bidentate ligand which can be the same as or different fromAr′—Ar″. Other examples of L include a diamine, including ethylenediamine, N,N,N′,N′-tetramethyl ethylene diamine, propylene diamine,N,N,N′,N′-tetramethyl propylene diamine, cis- andtrans-diaminocyclohexane, and cis- and trans-N,N,N′,N′-tetramethyldiaminocyclohexane; an imine, including 2[(1-phenylimino)ethyl]pyridine,2[(1-(2-methylphenylimino)ethyl]pyridine,2[(1-(2,6-isopropylphenylimino)ethyl]pyridine,2[(1-(methylimino)ethyl]pyridine, 2[(1-(ethylimino)methyl]pyridine,2[(1-(ethylimino)ethyl]pyridine, 2[(1-(isopropylimino)ethyl]pyridine,and 2[(1-(t-butylimino)ethyl]pyridine; a dimine, including1,2-bis(methylimino)ethane, 1,2-bis(ethylimino)ethane,1,2-bis(isopropylimino)ethane, 1,2-bis(t-butylimino)ethane,2,3-bis(methylimino)butane, 2,3-bis(ethylimino)butane,2,3-bis(isopropylimino)butane, 2,3-bis(t-butylimino)butane,1,2-bis(phenyl)mino)ethane, 1,2-bis(2-methylphenylimino)ethane,1,2-bis(2,6-diisopropylphenylimino)ethane,1,2-bis(2,6-di-t-butylphenylimino)ethane, 2,3-bis(phenyl)mino)butane,2,3-bis(2-methylphenylimino)butane,2,3-bis(2,6-diisopropylphenylimino)butane, and2,3-bis(2,6-di-t-butylphenylimino)butane; a heterocyclic compoundcontaining two nitrogen atoms, including 2,2′-bypyridine, ando-phenanthroline; a diphosphine, includingbis-(diphenylphosphino)methane, bis-(diphenylphosphino)ethane,bis-(diphenylphosphino)propane, bis-(dimethylphosphino)methane,bis-(dimethylphosphino)ethane, bis-(dimethylphosphino)propane,bis-(diethylphosphino)methane, bis-(diethylphosphino)ethane,bis-(diethylphosphino)propane, bis-(di-t-butylphosphino)methane,bis-(di-t-butylphosphino)ethane, and bis-(di-t-butylphosphino)propane; a1,3-diketonate (β-diketonate) prepared from a 1,3-diketone (β-diketone),including acetyl acetone, benzoyl acetone, 1,5-diphenylacetyl acetone,dibenzoyl methane, and bis(1,1,1-trifluoroacetyl)methane; a 3-ketonateprepared from a 3-keto ester, including acetoacetic acid ethyl ester; acarboxylate prepared from an aminocarboxylic acid, includingpyridine-2-carboxylate, 8-hydroquinolinate, quinoline-2-carboxylate,glycine, dimethyl glycine, alanine, and dimethylaminoalanine; asalicyliminates prepared from a salicylimine, including methylsalicylimine, ethyl salicylimine, and phenyl salicylimine; adialcoholate prepared from a dialcohol, including ethylene glycol and1,3-propylene glycol; a dithiolate prepared from a dithiol, including1,2-ethylene dithiolate and 1,3-propylene dithiolate. Preferably, L is aβ-diketonate, pyridine-2-carboxylate, a salicyliminate, or a derivativeof 8-hydroquinoline or quinoline-2-carboxylic acid.

Conjugated Luminescent Polymers Containing Metal Complexes

The halogenated aromatic monomer-metal complex is a precursor for ametal-complexed conjugated luminescent polymer, which can be ahomopolymer, a copolymer, a terpolymer, etc., and which can be preparedby any of a number of means. For example, the polymer can be prepared bya Suzuki coupling reaction, described in U.S. Pat. No. 6,169,163 (the'163 patent), column 41, lines 50-67 to column 42, lines 1-24, whichdescription is incorporated herein by reference.

In the present case, the Suzuki coupling reaction can be carried out byreacting, in the presence of a catalyst, preferably aPd/triphenylphosphine catalyst such astetrakis(triphenylphosphine)palladium(0), the halogenated aromaticmonomer-metal complex, preferably the bis(monohalogenated aromatic)complex, with a diboronated aromatic compound. The aromatic group of theco-monomer—which form structural units of the resultant polymer—may bethe same as or different from, preferably different from, the aromaticgroup associated with the halogenated aromatic monomer-metal complex.

It is also possible, and sometimes preferable, to prepare a polymerhaving structural units of more than two monomers by including in thereaction mixture a variety of halogenated and boronated co-monomersalong with the halogenated aromatic monomer-metal complex.

Polymerization can also be carried out by coupling one or moredihalogenated aromatic monomer-metal complexes with one or moredihalogenated aromatic compounds in the presence of a nickel salt, asdescribed in the '163 patent, column 11, lines 9-34, which descriptionis incorporated herein by reference.

The aromatic co-monomers that can be used to couple with the halogenatedaromatic monomer-metal complex is nearly endless but a representativelist includes, 1,4-diXbenzenes, 1,3-diXbenzenes, 1,2-diXbenzenes4,4′-diXbiphenyls, 1,4-diXnaphthalenes, 2,6-diXnaphthalenes,2,5-diXfurans, 2,5-diXthiophenes, 5,5-diX-2,2′-bithiophenes,9,10-diXanthracenes, 4,7-diX-2,1,3-benzothiadiazoles, diX triarylaminesincluding N,N-di(4-Xphenyl) anilines, N,N-di(4-Xphenyl)-p-tolylamines,and N-diXphenyl-N-phenylanilines, 3,6-diX-N-substituted carbazoles,2,7-diX-N-substituted carbazoles, 3,6-diX-dibenzosiloles,2,7-diX-dibenzosiloles, N-substituted-3,7-diXphenothiazines,N-substituted-3,7-diXphenoxazines,diX-N,N,N′,N′-tetraaryl-1,4-diaminobenzenes,diX-N,N,N′,N′-tetraarylbenzidines, diXarylsilanes, and2,7-diX-9,9-disubstituted fluorenes, including fluorenes in which the9,9-substituents combine to form a ring structure, and combinationsthereof, where each X is independently a halogen or a boronate,preferably bromo or chloro or boronate, more preferably bromo orboronate. As used herein, “boronate” refers to an aromatic fragment orcompound that is substituted with a borane group, a boronic acid estergroup, or a boronic acid group.

The resultant polymer has a backbone having structural units of a) anaromatic group which is also attached to a linking group that disruptsconjugation between the aromatic group and the metal complex fragment;and b) an aromatic comonomer, which forms a conjugated system with thearomatic group. The term “structural units” is used herein to refer tothe remnant of the monomer after polymerization. A structural unit ofthe aromatic group that is attached to the metal complex through alinking group is represented by the following structure:

where L, M, Ar′, and Ar″ are as previously defined, and at least one ofR′_(a) and R′_(b), preferably only one of R′_(a) and R′_(b), contains anaromatic group that is part of the polymer backbone, preferably a phenylgroup, a naphthalenyl group, or an anthracenyl group, more preferably aphenyl group; and a linking group, G, that disrupts conjugation betweenthe aromatic group and the metal complex fragment. The other of R′_(a)and R′_(b) is preferably a monovalent substituent, including H. Thus,where Ar is phenyl and R_(b) is H, the following structural unit isformed:

Similarly, a structural unit of a benzene-containing comonomer that isincorporated into the polymer backbone through the 1,4-positions is a1,4-phenylene group; a structural unit of a 9,9-disubstitutedfluorene-containing comonomer that is incorporated into the polymerbackbone through the 2,7-positions is a 9,9-disubstitutedfluorene-2,7-diyl group, where each R is a substituent, as illustrated:

Accordingly, the structural units corresponding to the above listedco-monomers are 1,4-phenylenes, 1,3-phenylenes, 1,2-phenylenes,4,4′-biphenylenes, naphthalene-1,4-diyls, naphthalene-2,6-diyl,furan-2,5-diyls, thiophene-2,5-diyls, 2,2′-bithiophene-5,5-diyls,anthracenes-9,10-diyls, 2,1,3-benzothiadiazoles-4,7-diyls, N-substitutedcarbazole-3,6-diyls, N-substituted carbazole-2,7-diyls,N-substituted-phenothiazine-3,7-diyls,N-substituted-phenoxazines-3,7-diyls, triarylamine-diyls includingtriphenylamine-4,4′-diyls, diphenyl-p-tolylamine-4,4′-diyls, andN,N-diphenylaniline-3,5-diyls, dibenzosilole-3,6-diyls,dibenzosilole-2,7-diyls, N,N,N′,N′r-tetraaryl-1,4-diaminobenzene-diyls,N,N,N′,N′-tetraarylbenzidine-diyls, arylsilane-diyls, and9,9-disubstituted fluorenes-2,7-diyls. It is to be understood that thepolymer, copolymer, etc. is not limited by the manner in which it ismade.

The resultant polymer has a conjugated backbone with metal complexationthat can be precisely controlled because preferably at least 90%, morepreferably at least 95%, and most preferably 100% of the structuralunits of the aromatic monomer-metal complex contain a metal complex thatis incorporated within the polymer backbone. Moreover, the metal complexis insulated from the conjugated polymer backbone due to the absence ofdirect delocalization between the ligand and the polymer backbone, whichinsulation preserves the luminescent properties of the metal complex.The terms “conjugated polymer” and “conjugated polymer backbone” areused to mean that the polymer backbone has electrons that aredelocalized throughout at least two adjacent structural units,preferably at least five adjacent structural units, more preferably atleast ten adjacent structural units.

Preferably, the ratio of structural units of halogenated aromaticmonomer-metal complex to structural units of the comonomer is preferablyat least 0.01:99.99, more preferably at least 0.1:99.9, and mostpreferably at least 1:99; and preferably not greater than 20:80, morepreferably not greater than 10:90.

The polymer of the present invention preferably has a weight averagemolecular weight M_(w) of at least 5000 Daltons, more preferably atleast 10,000 Daltons, more preferably at least 50,000 Daltons, and mostpreferably at least 100,000 Daltons; and preferably less than 2,000,000Daltons. M_(w) is determined using gel permeation chromatography againstpolystyrene standards.

The polymer of the present invention can be combined with one or moreother polymers to make a blend. Examples of suitable blending polymersinclude homo- or co-polymers (including terpolymers or higher) ofpolyacrylates, polymethacrylates, polystyrenes, polyesters, polyimides,polyvinylenes, polycarbonates, polyvinyl ethers and esters,fluoropolymers, polycarbazoles, polyarylene vinylenes, polyarylenes,polythiophenes, polyfurans, polypyrroles, polypyridines, polyfluorenes,and combinations thereof.

The polymer or blend of the present invention can be combined with asufficient amount of one or more solvents (hereinafter “solvent”) tomake a solution which is useful, for example, as an ink. The amount ofsolvent varies depending upon the solvent itself and the application,but is generally used at a concentration of at least 80 weight percent,more preferably at least 90 weight percent, and most preferably at least95 weight percent, based on the weight of the luminescent polymer, theoptional additives or modifiers, and the solvent.

Examples of suitable solvents for the polymer include benzene; mono-,di- and trialkylbenzenes including C₁₋₁₂-alkyl benzenes, xylenes,mesitylene, cyclohexylbenzene, and diethylbenzene; furans includingtetrahydrofuran and 2,3-benzofuran; 1,2,3,4-tetrahydronaphthalene;cumene; decalin; durene; chloroform; limonene; dioxane; alkoxybenzenesincluding anisole, and methyl anisoles; alkyl benzoates including methylbenzoate; biphenyls including isopropyl biphenyl; pyrrolidinonesincluding cyclohexylpyrrolidinone; imidazoles includingdimethylimidazolinone; and fluorinated solvents; and combinationsthereof. More preferred solvents include C₁₋₈-alkyl benzenes,cyclohexylbenzene, xylenes, mesitylene, 1,2,3,4-tetrahydronaphthalene,methyl benzoate, isopropyl biphenyl, and anisole, and combinationsthereof.

In a typical application, the ink formulation can be deposited on asubstrate such as indium-tin-oxide (ITO) glass having a holetransporting material disposed thereon. The solvent is then evaporated,whereupon the ink forms a thin film of the luminescent polymer. The filmis used as an active layer in an organic light-emitting diode (OLED)device, which can be used to make a display such as a self-emissive flatpanel display. The film is also useful in other electronic devicesincluding light sources, photovoltaic cells, and field effect transistordevices.

The following examples are for illustrative purposes only and are notintended to limit the scope of the invention.

Example 1 Preparation of Iridium (III)bis{2-[4′-(4″-bromophenoxy)phenyl]pyridinato-N,C²′}(acetylacetonate A.Preparation of 2-(4′-Phenoxy)phenylpyridine

4-Phenoxyphenylboronic acid (10.7 g, 0.05 mol) and 2-bromopyridine(11.58 g, 0.075 mol) were dissolved in 250 mL of THF followed byaddition of 2M NaCO₃ (60 mL) and tetrakis(triphenylphosphine)palladium(0) (0.29 g). The reaction mixture was boiled at reflux overnight andthen transferred into a separation funnel to remove the aqueous layer.The organic layer was removed in vacuo and the residue was elutedthrough a silica gel column, first with 1:1 chloroform and hexanemixture and then with pure chloroform to afford a pale yellow oil. HPLCshowed a purity of 99.5%. GCMS: M⁺=247.

B. Preparation of 2-[4′-(4″-Bromophenoxy)phenyl]pyridine

A solution of N-bromosuccinimide (NBS, 3.95 g, 22.2 mmol) in DMF (10 mL)was added to a solution of 2-(4′-Phenoxy)phenylpyridine (5.8 g, 23.4mmol) in DMF (100 mL) at room temperature. The reaction mixture wasstirred at 80° C. for 1 h. HPLC showed about 40% of the startingmaterial was converted. Additional NBS (1.55 g) was added and thereaction continued at 80° C. overnight. HPLC indicated a conversion of55%. Additional NBS (5 g) was added and the reaction was continued at80° C. for 1 h. HPLC showed complete conversion of the startingmaterial. After being cooled to room temperature, the reaction mixturewas poured into water (300 mL) with stirring whereupon NaOH solution (15mL of 50% (w/w)) was added into the mixture. The mixture was stirred atroom temperature for 2 h and was then filtered to collect the solid. Thesolid was washed with water and was re-crystallized from ethanol toprovide 5.5 g of the titled compound in white crystals. HPLC showed apurity of 98.6%. GCMS: M⁺=327.

C. Preparation of Iridium (III)bis{2-[4′-(4″-bromophenoxy)phenyl]pyridinato-N,C²′} μ-chloro-bridgeddimer

Iridium (III) chloride (% Ir=54.11, 1.5 g, 4.25 mmol) and2-[4′-(4″-bromophenoxy)phenyl]pyridine (3.5 g) were dispersed in2-ethoxyetanol (30 mL) at room temperature. The mixture was boiled atreflux under nitrogen for 20 h, at which time, a yellow solidprecipitated from solution. Methanol (100 mL) was added to the reactionmixture to complete the precipitation. The solid was collected byfiltration and was washed with methanol, 1N HCl, and ethanolsuccessively and then was dried in vacuo at 40° C. to provide 3.27 g ofyellow powder.

D. Preparation of Iridium (III)bis{2-[4′-(4″-bromophenoxy)phenyl]pyridinato-N,C^(2′}(acetylacetonate))

Iridium (III) bis{2-[4′-(4″-bromophenoxy)phenyl]pyridinato-N,C²′}μ-chloro-bridged dimer (1.05 g, 0.6 mmol) and sodium carbonate (1.0 g)were dispersed in 2-ethoxyethanol (60 mL). The mixture was degassed withnitrogen at room temperature for 15 min, whereupon 2,4-pentanedione(0.132 g, 1.32 mmol) was added together with 2-ethoxyethanol (20 mL).The mixture was refluxed for 1 h. TLC showed no dimer starting materialand the main product was found to be a green emissive material. Afterbeing cooled to room temperature, water (100 mL) was added toprecipitate the product. The yellow solid was collected by filtrationand dried in vacuo at 40° C. overnight. The crude product wasre-dissolved in methylene chloride and purified on a silica gel columneluted by methylene chloride to give 0.48 g of yellow powder, purtiy of99.5% by HPLC:

Example 2 Preparation of a Co-polymer Containing Iridium (III)bis[2-(4′-phenoxyphenyl)pyridinato-N,C²′](acetylacetonate)

Tetrakis(triphenylphosphine)palladium(0) (5 mg) and 2M aqueous sodiumcarbonate solution (11 mL) were added under nitrogen to a stirredmixture of 9,9-di(1-octyl)fluorene-2,7-diboronic acid ethylene glycolester (2.149 g, 4.04 mmol), 2,7-dibromo-9,9-di(1-octyl)fluorene (1.647g, 3.00 mmol), 3,7-dibromo-N-(4-n-butyl)-phenyl-phenoxazine (0.190 g,0.40 mmol),N,N′-(di(bromophenyl)-N,N′-di(9,9-dibutyl)fluorene-1,4-phenylenediamine(0.390 g, 0.40 mmol), iridium (III)bis{2-[4′-(4″-bromophenoxy)phenyl]pyridinato-N,C²′}(acetylacetonate)(0.188 g, 0.20 mmol), and Aliquat 336 (0.75 g) phase transfer catalystin toluene (50 mL). The reaction mixture was stirred at 101° C. undernitrogen for 16 h. Then, 9,9-di(1-octyl)fluorene-2,7-diboronic acidethylene glycol ester (20 mg) was added and the polymerization wascontinued under the same conditions for another 3 h. Bromobenzene (0.15g dissolved in 10 mL of toluene) was then added under the same reactionconditions for 2 h. Phenylboronic acid (0.4 g) andtetrakis(triphenylphosphine)palladium(0) (3 mg dissolved in 10 mL oftoluene) was added under the same reaction conditions for 4 h. Themixture was allowed to cool to about 50° C., the aqueous layer removed,and the organic layer washed with water. The resultant polymer solutionwas then poured into methanol (1.5 L) with stirring to precipitate paleyellow polymer fibers. These fibers were collected by filtration, washedwith methanol, and dried in vacuo at 50° C. overnight. The polymer wasre-dissolved in toluene and the solution passed through a column packedwith layers of celite and silica gel. The combined eluates wereconcentrated to about 100 mL, then poured into methanol (1.5 L) withstirring. The polymer fibers were collected and dried in vacuo at 50° C.overnight. The polymer was re-dissolved in toluene and re-precipitatedin methanol. After further filtration and drying, 2.26 g of pale yellowfibers were obtained. The weight average molecular weight (M_(w)) of thepolymer was measured by gel permeation chromatography (GPC) against thepolystyrene standards as 121,000 with a polydispersity index(M_(w)/M_(n)) of 3.78.

Example 3 Iridium (III)bis[2-(4′-phenoxyphenyl)pyridinato-N,C²′](acetylacetonate) Containing aFluorene copolymer II

The procedure described in Example 2 was followed except thatN,N-aiphenyl-3,5-dibromoaniline (0.3248 g, 0.80 mmol) was used insteadof dibromo-N-(4-n-butyl)-phenyl-phenoxazine andN,N′-(di(bromophenyl)-N,N′-di(9,9-dibutyl)fluorene-1,4-phenylenediamine(0.390 g, 0.40 mmol); the copolymer II was prepared in the yield of 2.13g.

Example 4 Light-Emitting Devices of a Metal Complex-Containing Polymer

A thin film of poly(ethylenedioxythiophene)/polystyrenesulfonic acid(commercially available from H. C. Starck and BAYTRON™ P conductingpolyer) was spin-coated on a ITO (indium tin oxide)-coated glasssubstrate, at a thickness of 80 nm. Then, a film of the metalcomplex-containing polymer described in Example 3 was spin-coated on thePEDOT film at a thickness of 80 nm from a solution in xylenes. Afterdrying, a thin layer (3 nm) of LiF was deposited on the top of thepolymer layer by thermal evaporation, followed by the deposition of acalcium cathode (10-nm thick). An additional aluminum layer was appliedby evaporation to cover the calcium cathode. By applying a bias (ITOwired positively) on the resultant device, bluish green light emissionwas obtained. The electroluminescent spectrum recorded at 200 cd/m²corresponds to the chromaticity coordinates of (x=0.240, y=0.270) in theCIE 1931 diagram. The brightness of the emission reached 200 cd/m² atabout 13 V with the luminance efficiency of 0.08 cd/A.

1. A halogenated aromatic monomer-metal complex compound comprising ahalogenated aromatic monomer fragment and a metal complex fragment andrepresented by the following formula (I):

where L is a bidentate ligand; M is Ir, Rh, or Os; Ar′ and Ar″ arearomatic moieties which may be the same or different with the provisothat at least one of Ar′ and Ar″ is heteroaromatic; and wherein R_(a)and R_(b) are each independently a monovalent substitutent or H, withthe proviso that at least one of R_(a) and R_(b) contains a halogenatedaromatic monomer fragment and a linking group that disrupts conjugationbetween the halogenated aromatic monomer fragment and the metal complexfragment; wherein the halogenated aromatic monomer-metal complexcompound is not a compound of formula (I) in which Ar′ represents abenzene moiety, Ar″ represents a pyridine moiety, and R_(a) represents aphenoxy group which may be substituted by halogen.
 2. The compound ofclaim 1 wherein Ar′ and Ar″ are each independently selected from thegroup consisting of benzene, pyridine, thiophene, and fluorene moieties;L is selected from the group consisting of diamines, imines, diimines,heterocyclics containing two nitrogen atoms, diphosphines,β-diketonates, 3-ketonates, salicyliminates, dialcoholates, anddithiolates; and R_(a) is -G-Ar—X, where G is selected from the groupconsisting of O, methylene, or oxymethylene, Ar is a benzene,napthalene, or anthracene moiety, and X is a halogen, provided that thecompound is not a compound in which Ar′ represents a benzene moiety, Ar″represents a pyridine moiety, G is O, Ar is benzene, and X is a halogen.3. The compound of claim 2 wherein Ar′ is a benzene moiety and Ar″ is apyridine moiety; L is selected from the group consisting ofβ-diketonates, pyridine-2-carboxylates, salicyliminates, derivatives of8-hydroquinoline, derivatives of quinoline-2-carboxylic acid; and Ar isa benzene moiety; and X is Br.
 4. The compound of claim 3 wherein L is aβ-diketonate.